RU2399947C1 - Natural gas odoriser - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: natural gas odoriser includes temperature-controlled service tank of odorising liquid with pressurisation branch pipe and odorant supply branch pipe, channel of pressurisation with high pressure gas, which is interconnected through service reduction gear and ejector with low pressure line, and through service reduction gear and pressurisation reduction gear with pressurisation branch pipe and through mixing valve with odorant supply branch pipe located in gas cavity of the tank and interconnected with low pressure line by means of switches through ejector or through odorant flow control. Odorant flow control includes central body installed in the body with possibility of axial movement by means of stock connected to drive mechanism controlled with pneumatic signal from pressure drop sensor of flow metre - contraction device in low pressure line. At that, passage area of the channel formed with central body and housing changes proportionally to gas flow in low pressure line.

EFFECT: minimising the number of movable odoriser elements, simplifying its construction, improving its operating reliability during odorisation of low gas flows and providing the supply of odorant vapours to the main line in direct ratio to gas flow in the main line.

6 cl, 3 dwg

Description

The invention relates to automatic control of fluid flow and can be used in various industries, for example, in the process of odorizing small gas flow rates, where a proportional flow of odorant to the gas line is required.

Methane-based natural gas is generally odorless. Before entering the consumer, the gas goes through certain stages of preparation, the main of which are cleaning, throttling, odorization. In the process of odorization, components with a pungent odor, which is easily determined by the organoleptic method, are added to the gas. Odorization is carried out in order to prevent gas leaks and ensure the safe operation of gas equipment. Ethyl mercaptan (C ₂ H ₆ S) and a mixture of natural mercaptans are used as odorants. It is possible to use other substances:

- two different complex (C1-C6) alkyl esters of acrylic acid; a combination or at least one compound from the group consisting of (C1-C8) mercaptans, (C4-C12) thiophenes, (C2-C8) sulfides or (C2-C8) disulfides;

a combination or at least one compound from the group consisting of (C1-C6) carboxylic acids, (C1-C8) aldehydes, (C6-C14) phenols, (C7-C14) anisoles or (C4-C14) pyrazines.

Natural gas moving along the main pipelines has a pressure p = 6 ... 12 MPa and a temperature of t≈10 ° C. Odorization of natural gas is usually performed on the GDS after its reduction to pressures p = 0.2 ... 0.6 MPa. There are two main ways to file an odorant:

- introduction (injection) into the gas stream of a liquid odorant with its subsequent evaporation;

- introduction of odorant vapor or a gas mixture containing odorant vapor into the gas stream.

A device for regulating the flow of odorant (patent No. 2173874, IPC G05D 7/00, publ. 2001.09.20) containing a flow tank with liquid odorant and an adjustable heater to turn the odorant into a vapor state, the heater is made in the form of flooded in the lower part the flow capacity of the recuperative heat exchanger, the input of which is connected to the hot end of the vortex energy separator, and the output to the neck of the Venturi pipe installed in the bypass line; On the branch of the pipelines for supplying hot gas to the heat exchanger and to the bypass line, a regulator is installed, made in the form of a flow distributor with a servo drive controlled by a signal from the control and control unit. The lower part of the tank is connected to the output of the metering pump, which is triggered by a signal from the sensor that controls the odorant level above the surface of the heat exchanger, and the upper part of the tank, above the spray separator, is connected to the pipe for removing odorant vapor, the output of which is connected to a utilizing ejector for mixing cold and used hot flows exiting the vortex energy separator.

Devices that supply liquid odorant to the gas stream (Danilov A.A., Petrov A.I. Gas distribution stations. St. Petersburg. Nedra Publishing House, 1997) are represented by plunger-type installations that perform discrete odorant delivery in proportion to gas flow . Since the amount of odorant introduced into the gas medium is 5-16 g per 10 ³ normal m ^{3 of} gas, the introduction of liquid odorant into the gas stream is used mainly with a stable and guaranteed high gas flow rate, Q≥100 nm ³ / h. At lower costs, purely technical problems arise with the dosing of small amounts of liquid and ensuring uniform (satisfactory technical specifications).

A device is known that contains a sensing element, a pressure transducer with a rod, a regulator, a measuring container with an odorant and a gas pipeline (USSR AS No. 219067, Mcl 2 G05D 16/06, publ. 1965). The introduction of liquid odorant into the gas stream is carried out under pressure using an adjustable metering pump. The required frequency of liquid injection into the gas pipeline is provided by a pneumatic time switch, the operation of which is determined by a spring-bellows gas pressure differential transducer.

A device for controlling the flow of odorant (patent No. 2153189, IPC G05D 7/00, published 2000.07.20), closest to the claimed and adopted as a prototype, containing a consumable container with an odorant, a sensing element, a metering pump. The metering pump is designed as a piston pneumatic hydraulic booster and provides a discrete metered odorant supply via a feedback signal with an odorized gas flow meter, the discharge line is connected through a cavitation venturi, in front of which a pressure sensor is installed, to flow tanks installed in series, connected to the gas pipeline through the main and reserve droppers, respectively, while the internal volume of the metering pump above the odorant supply piston, limited by a seal along the piston rod nya, communicated with the suction line through the check valve. However, the known device does not provide sufficient accuracy for regulating and supplying an odorant to a gas pipeline at low odorant costs and reliable protection against leakage of an odorant into the atmosphere, in addition, the device has a large number of moving parts, which reduces their reliability and can lead to leakage of an odorant and gas contamination of technical rooms .

The technical result to which the invention is directed is to simplify the design of the device by reducing movable elements, increasing operational reliability when odorizing small gas flows, preventing leakage of odorant into the atmosphere and ensuring ease of maintenance.

The technical result is achieved by the fact that in the natural gas odorizer, including the flow rate of the odorizing liquid with the boost pipe and the odorant supply pipe, the boost channel for high pressure gas, it is new that the boost channel for high pressure gas is communicated through a flow reducer and through an ejector with a low-pressure main pressure, and through the aforementioned flow reducer, the boost reducer with the boost nozzle and through the mixer valve with the odorant supply nozzle located in the gas cavity of the supply tank and communicated with the low-pressure line by means of switches through the aforementioned ejector or through an odorant flow regulator, the flow tank is thermostated.

The pressurization channel of the high-pressure gas is connected to the high-pressure natural gas pipeline.

The odorant vapor flow regulator is in communication with the flowmeter sensor in the low pressure line and with a valve in the odorant vapor supply channel through the control processor.

The odorant flow regulator contains a central body mounted in the housing, with the possibility of axial movement by means of a rod connected to a drive mechanism controlled by a pneumatic signal from the differential pressure sensor of the flow meter - a constricting device in the low pressure line, while the passage area of the channel formed by the central body and housing, varies in proportion to the flow of gas in the low pressure line.

The mechanism for moving the central body is made in the form of a chamber with a bellows connected to the rod of the central body, while the chamber cavity is in communication with a cavity of increased pressure, and the cavity of the bellows with a cavity of reduced pressure of the flow meter is a constricting device.

The mechanism for moving the central body can be made in the form of a chamber with a spring-loaded piston connected to the rod of the central body and dividing the chamber into cavities of high and low pressure, respectively communicated with cavities of high and low pressure of the flowmeter sensor - constricting device.

Figure 1 presents a diagram of an odorizer designed to odorize low gas flow rates.

Figure 2 - flow control odorant with a mechanism for moving the Central body in the form of a camera with a bellows.

Figure 3 - flow control odorant with a mechanism for moving the Central body in the form of a chamber with a spring-loaded piston.

The odorizer includes: a pressurization channel of high-pressure gas 1, in communication with a high-pressure natural gas pipeline; reduction unit 2, flowmeter - narrowing device (quantity counter) 3, differential pressure sensor 4, low-pressure output line 5, ejector 6, odorant flow regulator 7, rotameter (gas flow indicator gas + odorant) 8, control processor 9, cover 10 , thermostatically controlled supply tank 11, pipe 12 for taking the gas fraction from the tank 11, level sensor 13, temperature sensor 14, heat insulating shell 15, power supply 16, heater 17, boost pipe 18, filling and drain pipe 19, drain pipe 20, drain pipe 21, fuel line 22, control valve-mixer 23, solenoid valve 24, boost reducer 25, pressure sensor 26, flow reducer 27, control and shutoff valves - valves B ₁ -B ₄ , electrical switching lines 28, cover 29 of the camera of the regulator 30 ( 2 and 3), the bellows 31 of the pressure regulator 7, the piston 32 of the regulator 7, the seal 33, the central body 34, the supply channel of the odorant 35 to the low pressure pipe 5, the rod 36 and the spring 37 of the pressure regulator 7.

The proposed device provides a pulsed or continuous supply of the gas fraction of the odorant in proportion to the consumption of natural gas by the consumer.

The initial state of the system: the tank 11 is filled with an odorant to the working level (the level is located below the pipe 12); the liquid in the thermostatic flow tank 11 is at a certain temperature and is kept constant with the help of temperature sensors 14 and the controlled mode of operation of the heater 16. When gas is supplied to the consumer, the reduction system maintains a constant gas pressure in the low-pressure line 5 (p ~ 0.105 MPa), while thermostated the supply tank 11 with an odorant is under a certain excess pressure, which is the sum of the saturated vapor pressure of the odorant and the gas pressure determined by the mood Coy consumable gear 27. At constant temperature in the vessel 11 and the vapor pressure of the odorant quantity per unit volume of the gas mixture over the liquid to be well defined and can be found at known densities of components (thermal equation of state) from thermodynamic relationships. The amount of odorant in the mixture depends only on the vapor pressure. If we use the ideal gas model in the calculation, then at low to moderate pressures, the ideal gas model agrees well with natural gas.

The device can operate in two modes:

- 1st mode - the supply of a gaseous odorant to the highway 5 using the ejector 6;

- 2nd mode - the supply of a gaseous odorant to the highway 5 through the flow regulator of the odorant 7.

When the device is operating in the first mode, valve B _{4 is} closed. Gas from the high-pressure line through channel 1 through the flow reducer 27 enters the ejector 6, and through the reducer 27 and the boost reducer 25 to the boost nozzle 25 and the mixer valve 23. The mixture of odorant vapor with gas from the tank 11 is mixed with natural gas in the control the mixer mixer 23 and then through the open valve B ₅ enters the ejector 6 as a passive working fluid. The active working fluid of the ejector 6 is the gas coming from the high-pressure line. The pressure of the gas entering the inlet to the ejector 6 is determined by the flow reducer 27, and its adjustment is determined by the pressure sensor 26. The amount of incoming odorant is controlled by a mixer valve 23 by changing the amount of gas coming from the main and from the tank 11 with an odorant. It is possible to dose the amount of odorant entering the ejector 6 using an electrovalve 24. The flow of odorant entering the supply channel of the odorant 35 to the low-pressure line 5 is controlled by a rotameter 8.

When the device according to the second embodiment, the valve B ₅ closes, and the valve B ₄ opens. From the steam cushion of tank 11 through pipe 12, a mixture of odorant and gas vapors containing a certain amount of odorant per unit volume (this amount is determined by the pressure of saturated odorant vapors) enters the mixer valve 23 and can be additionally diluted with natural gas coming from the high-pressure line through gearbox 27. Next, the gas mixture (odorant + gas) enters the flow regulator of odorant 7, which ensures the flow of odorant to line 5 in proportion to the flow of natural gas measured flow omer - narrowing device 3.

The arrival of the odorant in proportion to the gas flow rate can be realized in the regulator 7, the embodiments of which are presented in FIGS. 2 and 3. The flow meter — the constricting device 3 generates an output signal — pressure drop Δp. According to the equations of hydraulics, with the geometry of the constricting device unchanged, the gas flow will be directly proportional to Δp, if the pressure differential is supplied to the pressure regulator chamber 30 equipped with a piston 32 and a spring 37 (Fig. 3), or a bellows 31, then the piston 32 or the bellows 31 will move will be directly proportional to Δp. The rod 36 of the piston 32 or bellows 31 through a seal 33 is connected to a central body 34 moving inside the cylindrical shell of the flow regulator 7, while the flow cross section of the gas mixture (gas + odorant pairs) through the odorant flow regulator 7 will change. Direct proportional dependence of the odorant flow from Δp will occur if the central body 34 of the regulator 7 is profiled as a paraboloid of revolution (parabola of the 4th degree).

Thus, the proposed device has a minimum number of movable elements, which allows to simplify the design of the odorizer, to simplify its maintenance and at the same time increase the reliability of its operation when odorizing low gas flow rates, ensuring the supply of odorant vapors to the pipeline, directly proportional to the gas flow to the pipeline.

Claims (6)

1. Natural gas odorizer, including the supply capacity of the odorizing liquid with a boost pipe and an odorant supply pipe, a boost channel for high-pressure gas, characterized in that the boost channel for high-pressure gas is communicated through a flow reducer and through an ejector with a low-pressure line, and through the aforementioned flow pressure reducer and pressure reducer with boost nozzle and through a mixer tap with an odorant supply nozzle located in the gas cavity of the supply tank and in communication with the low pressure line by means of switches through the aforementioned ejector or through an odorant flow regulator, the flow tank is thermostatically controlled. 2. The natural gas odorizer according to claim 1, characterized in that the pressurization channel of the high-pressure gas is in communication with the high-pressure natural gas pipeline. 3. The natural gas odorizer according to claim 1, characterized in that the odorant flow regulator is in communication with a flow meter - a constricting device in the low pressure line and with a valve in the odorant vapor supply channel through the control processor. 4. The natural gas odorizer according to claim 1, characterized in that the odorant flow regulator comprises a central body mounted in the housing with axial displacement by means of a rod connected to a drive mechanism controlled by a pneumatic signal from the differential pressure sensor of the flow meter - a constricting device in the low line pressure, while the area of the passage section of the channel formed by the Central body and the body, varies in proportion to the gas flow in the low pressure line. 5. The natural gas odorizer according to claim 4, characterized in that the mechanism for moving the central body includes a chamber with a spring-loaded piston connected to the rod of the central body and dividing the chamber into cavities of high and low pressure, respectively connected with cavities of high and low pressure of the flowmeter sensor - narrowing device. 6. The natural gas odorizer according to claim 4, characterized in that the mechanism for moving the central body includes a chamber with a bellows connected to the rod of the central body, while the chamber cavity is in communication with an increased pressure cavity, and the bellows cavity with a reduced pressure cavity of the flow meter is a constriction device .

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